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  1. Practice
  2. Functional Programming
  3. Introduction
  4. Update List
  5. Discussions

Update List

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votes

  • gmrodgers + 1 comment

    f arr = map abs arr

    • tongda + 0 comments

      actually you could omit arr as follow:

      f = map abs

  • PaGrom + 0 comments

    Clojure:

    (fn[lst]
    (map #(Math/abs %) lst))

  • balintant + 0 comments

    Haskell

    -- Enter your code here. Read input from STDIN. Print output to STDOUT

f arr = [abs x | x <- arr]-- Complete this function here

-- This section handles the Input/Output and can be used as it is. Do not modify it.
main = do
   inputdata <- getContents
   mapM_ putStrLn $ map show $ f $ map (read :: String -> Int) $ lines inputdata

  • Jack_Lee1_ + 5 comments

    For Scala

    import scala.math._
def f(arr:List[Int]):List[Int] = arr.map((a:Int) => abs(a))

    I feel it was a bit of cop out using the abs() function. Does anyone have a method to solve it using something tail recursive?

    • luizpericolo + 1 comment

      Here you go:

      def f(arr:List[Int]):List[Int] = {
    def absList(absed: List[Int], unabsed: List[Int]): List[Int] = {
        unabsed match {
            case Nil => absed
            case x :: xs => {
                x match {
                    case v if v < 0 => absList(absed :+ v * -1, xs)
                    case v => absList(absed :+ v, xs)
                }
            }
        }
    }
    absList(Nil, arr)
}

      Feel free to ask if you have any doubts.

      • bayalla_abdelka1 + 0 comments
        def fabs(arr:List[Int]):List[Int] = {

  def loop(arr:List[Int],acc:List[Int]):List[Int] = arr match {
    case Nil => Nil
    case h :: tail =>  h.abs :: loop(arr tail,acc)
  }
    
  loop(arr,List()) 
}
    • vestail + 0 comments

      or just

      arr.map(Math.abs)
    • MartinRosenberg + 0 comments

      Generally, I'd avoid cluttering the namespace with a wildcard import, especially given only one member of it is actually being used. Also, for members of scala, you can actually drop scala.:

      def f(arr: List[Int]): List[Int] = arr map math.abs
    • MartinRosenberg + 0 comments

      To avoid using math.abs:

      def f(arr: List[Int]): List[Int] = arr map (x => x * x.signum)

      And if you wanna do that with tail recursion:

      def f(arr: List[Int]): List[Int] = {
  @annotation.tailrec
  def run(i: Int, res: List[Int]): List[Int] = arr.length match {
    case `i` => res
    case _   => run(i + 1, res :+ arr(i) * arr(i).signum)
  }
  run(0, List.empty[Int])
}
    • sao_rahul + 0 comments

      "def f(arr:List[Int]):List[Int] = arr.map(x => if (x < 0 ) -x else x )"

  • pratyoosh_sharma + 2 comments

    Scala noob here, any comments if this is a valid solution scala def abs(x:Int):Int = { if(x<0) x * -1 else x } def f(arr:List[Int]):List[Int] = { arr.map(x=> abs(x)).toList
    }

    • martinez_calvo_1 + 2 comments

      Instead of to declare abs function, you can use Math.abs, and also the .toList is not necessary because the map function returns in this case a List

      Here is my solution

      arr.map(Math.abs(_))

      • fazzdev + 0 comments

        even better with arr.map(math.abs)

      • baranoob + 1 comment

        How about arr.map(_.abs)?

        • leongfeng + 0 comments

          I think this is a good solution.

    • numerocinquo + 0 comments

      def f(arr:List[Int]):List[Int] = for(i <- arr) yield(i.abs)

  • ddenisovdanila + 0 comments

    Erlang solution:

    main() ->
	L = fun F(Acc) -> case io:fread("", "~d") of eof -> lists:reverse(Acc); {ok, [N]} -> F([abs(N) | Acc]) end end,
    [io:fwrite("~p~n", [X]) || X <- L([])].

  • patrickwherrmann + 0 comments

    Here's kind of a funny solution:

    main = interact $ filter (/= '-')

  • johanirvall + 0 comments

    Full solution including IO-handling in F#:

    Seq.initInfinite (fun _->System.Console.ReadLine())
|> Seq.takeWhile ((<>) null)
|> Seq.map (int>>abs)
|> Seq.iter(printfn "%d")

  • rauan_assis + 0 comments

    My Elixir solution:

    defmodule Solution do
  def main() do
    IO.read(:stdio, :all)
    |> String.split()
    |> Enum.map(&String.to_integer(&1))
    |> get_absolutes
  end

  def get_absolutes(list) do
    Enum.each(list,
      fn(x) ->
        if x < 0, do: IO.puts(x * -1), else: IO.puts(x)
      end
    )
  end
end

Solution.main()

  • adrielradicchi + 0 comments

    My Elixir Solution 

    IO.read(:stdio, :all)
    |> String.split
    |> Enum.map(&String.to_integer(&1))
    |> Enum.map(&(abs(&1)))
    |> Enum.map(&IO.puts(&1))
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